Aroma profiles of shalgam: Effect of purple carrot (Daucus carota) amount

Abstract Shalgam is a fermented product characterized by its color and aroma compounds. However, there is no standard regarding the amount of use of purple carrot, which is the major raw material in production and affects the fermentation and aroma compounds of the product. This present research was designed to examine the effect of purple carrot concentrations on aroma compounds, which are one of the most important characteristics that reflect the quality characteristics of shalgam and affect consumer preferences. Aroma compounds in shalgam juices produced using five different amounts of carrots were analyzed by gas chromatography‐flame ionization detector‐mass spectrometry (GC‐FID‐MS). As expected, since the difference between the produced shalgam beverages was only the amount of purple carrots, a qualitative similarity and a quantitative difference were determined in the aroma profiles in general. In the aroma categories defined, terpenes (26 compounds) were the most abundant compounds, followed by esters (17 compounds) and higher alcohols (11 compounds). 88 aroma compounds have been identified in shalgam, and a total of 28 ACs, including 7 terpenes, 7 esters, 3 alcohols, 4 volatile acids, 3 volatile phenols, 1 lactone, 1 norisoprenoid, and 2 naphthalenes, were detected for the first time. The concentration of aromas in the samples varied from 5471.5 to 6490.1 μg/L (p < .05). According to principal component analysis, it was determined that the correlation between the position of the shalgam samples in the coordinate system and the aroma groups was significant. This study shows that purple carrots also affect the aroma compounds of shalgam beverages.

non-volatile (free sugars, phosphates, nitrogenous compounds, etc.) compounds from black carrots (Alabran & Mabrouk, 1973;Ekinci et al., 2016;Tanguler et al., 2017).Some researchers have reported that the terpene compounds of black carrots, which have an important place in the aroma compounds of shalgam, usually have a harsh and bitter taste (Ekinci et al., 2016;Tanguler et al., 2017).Similarly, it has been reported that black carrot contributes to flavor development by playing an important role in the conversion of sugar to organic acids during fermentation (Tanguler et al., 2017).
However, it has been reported recently that some producers do not use turnip radish as raw materials by making some modifications in production but only use purple carrots and other raw materials.Purple carrot is an important part of the raw materials utilized in shalgam beverage manufacture (Erten et al., 2008;Tanguler & Erten, 2012).
Aroma is one of the most significant sensorial attributes, reflecting the quality characteristics of shalgam, which is made up of a mixture of volatile molecules with various odor characteristics.Aroma compounds (ACs) are compounds that evaporate easily in ambient conditions.The molecular weight of these compounds is less than 300 Da (Angerosa, 2002).Following changing consumer demands in recent years, the examination of the volatile profiles of the products tends to be one of the primary characteristics to be considered in the progress of fermented food.
Especially the amount of black carrot added is crucial, as it determines the acidity and color levels that determine the sourness of the final beverage.Moreover, the unique aroma properties of shalgam are greatly affected by the raw materials used in its manufacture and the fermentation conditions carried out.Black carrot, in particular, has an important impact on the aroma of shalgam beverage, both because it is a fundamental raw material in the production of shalgam beverage and because of its unique aroma (McFeeters, 2004;Tanguler et al., 2014).Although the number of studies on shalgam beverage, which is stated to have positive effects on health, has increased in recent years, there are a limited number of studies on the flavoring substances in this product.These studies were realized on the effect of the production methods (traditional process, fast process, and usage of starter culture) on the aroma profile of shalgam (Tanguler et al., 2017), the effects of pasteurization and storage conditions on the aroma compounds present (Kirlangic et al., 2021), and the next-generation sequencing of shalgam beverage aroma influencing microbiota (Ekici et al., 2021).However, no published studies have been found so far on the effect of the amount of black carrot on the composition of the aroma profiles of shalgam.The present research aimed to compare the effects of the amount of purple carrot on the composition of ACs of shalgam.Therefore, in the shalgam produced using different amounts of purple carrots, ACs were determined and quantified by GC-MS and GC-FID, which are widely used.

| Materials and chemicals
Black carrots, bulgur flour (setik), and turnip radish used in the production of shalgam beverages were obtained from the Adana fruit and vegetable market.Baker's yeast and salt were obtained from the Migros market.Dichloromethane, anhydrous sodium sulfate, lactic acid, acetic acid, citric acid, glucose, and fructose were bought from Merck KGaA (Darmstadt, Germany).

| Shalgam production
Shalgam beverage production was done with the traditional process with some modifications (Erten et al., 2008).In brief, setik, rock salt, and sourdough were added at rates of 30, 2, and 2 g/L, respectively.
Then, drinking water was added and kneaded until it reached dough consistency.The dough was fermented in 40-L plastic drums at 25°C (Ι.Fermentation).The dough fermentation was carried out for 72 h, and then it was diluted at the end of the process.After this, it was carried out with the main fermentation, also known as carrot fermentation.The first fermentation broth was mixed with different amounts (100, 125, 150, 175, and 200 g/L) of sorted and chopped purple carrots and rock salt (10 g/L).In other words, the fermentation broth was transferred to five separate tanks in equal amounts to carry out carrot fermentation (2nd fermentation).Shalgam tanks were named Shalgam-100PC, Shalgam-125PC, Shalgam-150PC, Shalgam-175PC, and Shalgam-200PC, respectively.Glass tanks with a volume of 9 L were used, and the tank was closed before fermentation, which was carried out at 25°C.Sampling is described in Figure 1.
No pre-treatment was applied to purple carrots other than shredding in standard sizes and cleaning.In each fermentation, bulgur flour, rock salt, drinking water, and sourdough were used in the same amount and quality as standard.When the fermentation ended, the shalgam beverages were removed from the residue, bottled, and placed in cold storage at +4°C.They were kept in the same place throughout the analysis.Before the analyses, parallel samples were combined, and analyses were carried out using these samples.Aroma analyses were carried out in three parallels.

| HPLC determination of lactic, acetic, and citric acids and sugars
Lactic, acetic, and citric acids and sugars (glucose and fructose) in shalgams were determined by using the HPLC "Shimadzu LC-20AD, Japan".The shalgam beverages removed from the residue were firstly filtered (0.45 and 0.22 mm filters; "Millipore, Darmstadt") and then injected into the column.The column used in the analysis is a "300 × 7.8 mm" long Bio Rad brand (USA) Aminex-HPX 87H column.
The column temperature was 50°C, and high-purity water and sulfuric acid were used as eluent (0.5% mmol sulfuric acid-water).The flow ratio was set at 0.6 mL per minute, and a UV detector for organic acids and a refractive index detector for sugars were used.The amount of sugar was calculated using an RI detector (Shimadzu).On the other hand, the amounts of organic acids were calculated using a UV detector (Shimadzu;Tanguler & Erten, 2012).Identification of sugar and organic acid peaks was performed using certified standard materials ("Lactic acid Merck-100366," "acetic acid Merck-818755," and "citric acid Merck-100244," and "glucose Merck-108337" and "fructose Fluka-47740").The emergence time and spectra of the peaks were identified by comparison with standard substances.To calculate the concentration of the peaks, five different concentrations of standard substances were injected into the system, and the resulting calibration curves were used for this purpose.

| Liquid-liquid extraction carried out in shalgam samples
The extraction procedure performed in this study was designed in light of our previous article (Tanguler et al., 2017).According to Sen (2021), ACs were extracted in dichloromethane (CH 2 CI 2 ).Before extraction, the samples, 4-nonanol (internal standard) and dichloromethane, were stirred for 30 min at 4°C and their amounts were 40 μg and 40 mL, respectively.The mixing process was carried out under nitrogen gas conditions.After that, centrifugation (9000 g, 15 min) was applied to the obtained mixtures at 4°C.The pooled organic extract was obtained by dehydration with Na 2 SO 4 .The organic extracts were then concentrated to 0.5 mL at 45°C in a "Vigreux column."Extraction was performed in triplicate for each produced shalgam.The concentrations of ACs are stated as 4-nonanol equivalent (Sen, 2021).The peak area ratio was adjusted with the response factors of each AC, and they were calculated from the intensity ratio of each compound to 4-nonanol.
F I G U R E 1 Shalgam production by traditional method.Shalgam-100PC, 100 g/L purple carrot addition; Shalgam-125PC, 125 g/L purple carrot addition; Shalgam-150PC, 150 g/L purple carrot addition; Shalgam-175PC, 175 g/L purple carrot addition; Shalgam-200PC, 200 g/L purple carrot addition.Flavor 2L) and the instrument's internal library created from the previous laboratory studies.Some of the compounds were quantified and confirmed by utilizing the internal standard.The retention indexes of the ACs were determined based on an n-alkane series.
The LOQ value varies between 2.4 ng/g and the LOD value varies between 0.92 ng/g in the calculation made on the 4-nonanol internal standard.As a result, the realized liquid-liquid extraction method has low LOD and LOQ values.

| Statistical analysis
The XLStat (2022) (Addinsoft) package program was used in the statistical analysis.Quantities and standard deviations of the data were found using MS Office Excel.Analysis of variance and Duncan's multiple comparison test methods were used to evaluate differences.
Differences of p < .05were considered significant.Principal component analysis (PCA) was also performed.The data matrix consisted of samples and chemical classes of aroma compounds as observations and variables.

| RE SULTS AND D ISCUSS I ON
Organic acids, especially lactic acid, found in fermented products are important chemical components that contribute to the taste and aroma of the products (Tanguler & Erten, 2012).During the production of shalgam beverages, especially in the second fermentation, the sugars in the raw materials are mainly converted into lactic acid by mostly homofermentative and also heterofermentative lactic acid bacteria (Erten & Tanguler, 2012).Lactic and acetic acid concentrations in the samples were determined to be between 4.18-6.6g/L (p < .001)and 0.55-0.65 mg/L (p > .05),respectively.
On the other hand, citric acid could not be detected in any of the shalgam samples.In addition, the amounts of fructose and glucose in the samples were determined between 50.5-57.1 mg/L (p > .05)and 42.6-60.5mg/L (p < .05),respectively.
Tanguler and Erten (2012) determined the lactic acid and acetic acid contents of shalgam beverages produced by different methods, collected from the Adana market, between 2.66-4.74g/L and 0.35-1.16g/L, respectively.The researchers also could not detect citric acid in two samples but found citric acid between 71.5 and 3417 mg/L in the other samples.In addition, it is reported that in the shalgam standard existing in Turkey, the amount of lactic acid in shalgam beverages should be between 4.5 and 5.5 g/L (TSE, 2003).Ekinci et al. (2016) stated that lactic acid, acetic acid, fructose, and glucose amounts in shalgams were 8.9 g/L, 1.29 g/L, 104 mg/L, and 41 mg/L, respectively.Our results state that the lactic acid and acetic acid levels of shalgam beverages are in good agreement with TSE ( 2003) and Tanguler and Erten (2012).On the other hand, it was found to be lower than the values reported by Ekinci et al. (2016).
Compared to the raw materials used in shalgam beverage production, the amounts of glucose and fructose in shalgam beverages are generally at low levels.The most important reason for this is the use of these sugars mainly by lactic acid bacteria and also by yeasts during the two-stage fermentation (Ekinci et al., 2016;Tanguler & Erten, 2012).Tanguler and Erten (2012) stated that glucose and fructose levels in shalgam beverages produced by different methods collected from the Adana market were generally below 200 mg/L and were between 117-1902 mg/L and 60-1310 mg/L, respectively.The glucose and fructose results obtained in this study were generally found to be slightly lower than the results reported by the abovementioned researchers.

| Aroma compounds of shalgam samples
Although there have been few studies on ACs in shalgams (Kirlangic et al., 2021;Tanguler et al., 2017), no previous study has been found on the effect of adding different amounts of purple carrot.
Therefore, this study is the first to focus on this topic, and ACs were determined by GC-FID-MS.A total of 88 ACs composed of 26 terpenes, 17 esters, 11 alcohols, 10 volatile acids, 9 volatile phenols, 6 lactones, 2 norisoprenoids, 5 naphthalenes, and 2 aldehydes and ketone were identified in the shalgam samples (Table 1).Terpenes were the most abundant of the identified categories of ACs, followed by esters.
The dominant aroma compounds in terms of quantity were higher alcohols (2950 and 3865 μg/L), followed by terpenes (1006  the SPME/GC-MS method to determine the effect of natural microflora on aroma compounds during 20-day shalgam fermentation. In another study, the effect of pasteurization and storage on the aroma profile was determined (Kirlangic et al., 2021).These researchers stated that they detected 60, 24, and 32 different ACs in shalgams, respectively.
An important part of the ACs in shalgam comes from purple carrot, which is the main raw material used.In the current study, partially different results were obtained from the studies on carrots, the main raw material used in shalgam production.

| Terpenes
It was defined in this research that terpenes were quantitatively the second group of ACs in shalgams.Similarly, Keser et al. (2020) and Keskin et al. (2021)

TA B L E 1 (Continued)
Nineteen of the 26 terpenes determined and quantified in shalgams in the study carried out are terpenes determined in previous studies (Ekici et al., 2021;Tanguler et al., 2017).However, transβfarnesene (green apple), α-zingiberene (ginger), (Z)γ-bisabolene (flowery), (E)γ-bisabolene (balsamic), nerol (citrus, orange), transcarveol (spicy), and squalene (floral) are important as they are the first time detected in shalgam.It can be said that the reason for this is the raw materials used in production, the compounds and microorganisms that pass from these raw materials to the fermentation medium, and the fermentation process.
In the present study, α-terpinolene (which gives oil, anise, and mint flavor) is the volatile component with the highest ratio (32.81-39.03%) of all terpenes, followed by 1-borneol, (E)γ-bisabolene, and squalene.Their amounts were determined as 368-428, 61-124, 39-142, and 70-106 μg/L, respectively (Table 1).In research investigating the effects of processing and storage methods on the ACs of shalgam, results similar to the data obtained in this study were reported (Kirlangic et al., 2021;Tanguler et al., 2017).Similarly, Ekici et al. (2021) determined the presence of terpinolene from the 10th day of shalgam fermentation and reported the importance of terpenes, a group of ACs in shalgam.Moreover, the addition of a different amount of purple carrot significantly (p < .05)affected the amount of relative and total terpenes.

| Esters
Esters are compounds responsible for the floral and fruity features of many fruits, vegetables, and drinks.Esters in fermented products such as shalgam and wine come from raw materials used in production and are formed as a result of the enzymatic activity of microorganisms during fermentation (Sen, 2021;Tanguler et al., 2017).A total of seventeen ester compounds were identified in all the shalgams.Seven of them (ethyl lactate, dimethyl glutarate, ethyl octadecanoate, ethyl oleate, ethyl linoleate, ethyl vanillate, and ethyl linolenate) were not isolated and identified from shalgam in previous studies and were identified for the first time.
In addition, in another study, 4 out of 34 ACs in pasteurized and unpasteurized shalgams were determined to be esters (Kirlangic et al., 2021).
The concentration of all relative ester compounds is significantly (p < .05)affected by the addition of the different amounts of purple carrot (Table 1).Regarding the total amounts of esters, Shalgam-100PC and Shalgam-200PC showed greater amounts of esters than other samples, 419.5 and 417.0 μg/L, respectively (Table 2).On the other hand, the ester contents of the Shalgam-125PC, Shalgam-150PC, and Shalgam-175PC samples were similar (p > .05).In previous studies, the total ester content in shalgam was found to be between 105 and 173 μg/L in lower amounts, especially with the effect of the difference in the production method (Tanguler et al., 2017).In our study, the amount of ester determined in shalgams was found to be higher.This difference may depend on the production process used, the raw materials used in the manufacture, and the starter culture used.
TA B L E 2 Total concentrations of aroma groups of shalgam (μg/L).

| Higher alcohols
Many higher alcohols are synthesized during lactic acid+ethanol fermentations and contribute to the shalgam ACs.In the present study, eleven higher alcohols were described, and these are the main ACs with an amount of 52-59% in all shalgam beverages.Similarly, Ekici et al. (2021) reported that the main groups of quantitative ACs in shalgams are terpenes and alcohols.Total amounts of higher alcohols changed between 2950 μg/L (Shalgam-125PC) and 3865 μg/L (Shalgam-200PC), and they were the most abundant aroma group regarding their concentrations (Table 2).Tanguler et al. (2017) determined higher alcohols at lower concentrations (between 1728 and 3031 μg/L) in shalgams produced by different processes and the addition of autochthonous starter culture.While the lowest value was determined in shalgam produced by the traditional method, the highest value was reported in shalgam obtained with Lactiplantibacillus plantarum inoculation.In the present study, the addition of increasing amounts of purple carrots generally increased total alcohol content (exception for Shalgam-100PC).
The concentration of higher alcohols was highest in Shalgam-200PC, suggesting that the amount of shalgam may affect the number of higher alcohols.Among them, isoamyl alcohol stands out significantly in terms of amount.At the same time, isoamyl alcohol had the highest concentration in all samples (1484-2206 μg/L) and the concentration was highest in Shalgam-200PC (Table 1).This compound is one of the branched-chain primary alcohols and is extricated as a secondary product of yeast metabolism.In many studies, isoamyl alcohol has been implicated as responsible for the cheese-like ACs of fermented products (Celebi Uzkuc et al., 2020).
Following isoamyl alcohol, the compounds with the highest concentration in all samples were benzyl alcohol, 2-methoxy-phenyl-ethanol, and 2-phenyl ethanol.In previous research, the presence of isoamyl alcohol, 2-methoxy-phenyl-ethanol, and 2-phenyl ethanol (phenethyl alcohol) was determined, but the presence of benzyl alcohol was not in shalgam (Tanguler et al., 2017).
In shalgams, benzyl alcohol with a citrus-sweet-like odor was determined at a concentration between 399 and 461 μg/L (Table 1) and gives shalgam a citrus-sweet-smelling aroma.2-phenyl ethanol and benzyl alcohol are compounds that give floral (roses) and citrussweet aroma formation, respectively, in fermented drinks (Celebi Uzkuc et al., 2020).However, while Kirlangic et al. (2021) determined 2-hexadecanol in shalgam, it could not be determined in our study.Thus, it is seen that different fermentation conditions and raw material amounts show different tendencies for higher alcohols.In addition, the amounts of purple carrots affected the higher alcohol concentration (p < .05).

| Volatile acids
Volatile acids occur naturally in fruits, vegetables, and their juices, as well as being formed during fermentation.In fermentation, it is based on oxidation or reduction reactions of aldehydes, especially with microbial enzymes (α-keto acid dehydrogenase) synthesized by lactic acid bacteria (Tanguler et al., 2017).The total amount of volatile acids ranged from 325 to 375 μg/L in Shalgam-100PC, Shalgam-125PC, and Shalgam-150PC samples; on the other hand, this value was 269 and 287 μg/L in Shalgam-175 BC and Shalgam-200PC, respectively (Table 2).Kirlangic et al. (2021) reported the total amount of volatile acid in unpasteurized shalgam as 89.5 μg/L.
In previous research, these values were between 69.3 and 163 μg/L in all samples (Tanguler et al., 2017) and were found to be lower than the values obtained in our study.A decrease in total volatile acid amount was observed with increasing purple carrot addition, and it was found to be statistically significant (p < .05).It constitutes 4.15-6.49% of all ACs.
In the purple carrot studies, a volatile acid, hexanoic acid, was found and its amount was expressed as 133 and 141.7 μg/kg.They reported that acetic acid could not be determined in fresh carrots (Keser et al., 2020;Keskin et al., 2021).In contrast to the other two studies, Polat et al. (2022) stated the presence of four volatile acids (acetic acid, hexanoic acid, octanoic acid, and nonanoic acid) in purple carrots, with this volatile acid comprising only 1.23% of all ACs.
Therefore, it can be said that some of these compounds determined in shalgam originate from purple carrot.
Ten volatile acids were determined in all shalgam samples.
In all samples, the main volatile acid compounds were heptanoic acid (ranging from 117.8 to 153.1 μg/L) and hexanoic acid (ranging from 63.6 to 92.6 μg/L), respectively (p < .05;Table 1).Both compounds are characterized as odorous and plastic-like (Schreiner et al., 2018).Other ones are decanoic, acetic, butanoic, isovaleric, 2-methyl-butanoic, pentanoic, octanoic, and dodecanoic acid.Kirlangic et al. (2021) identified 2 acids (acetic acid and nonanoic acid) in shalgam samples.Similarly, in a previous study, five different ACs were found: butanoic acid, isovaleric acid, pentanoic acid, hexanoic acid, and heptanoic acid (Tanguler et al., 2017).However, in our current study, 2-methyl-butanoic acid, octanoic acid, decanoic acid, and dodecanoic acid were detected for the first time in shalgam.Therefore, as stated above, it can be said that the volatile acids determined other than octanoic acid originate from fermentation.1).4-Methyl-2,6-di-tert-bu tyl-phenol has been associated with burnt-plastic odors, while eugenol provides a clove-like fragrance.Eugenol is an important aromaactive substance in some fruits and has a low detection threshold (6 μg/L) in aqueous media (Tanguler et al., 2017).Besides guaiacol, 2-methoxy-4-vinyl-phenol and cis-isoeugenol are volatile phenols that have not been identified so far in shalgams and are reported for the first time in a study.In a previous study, in addition to eugenol, p-vinyl guaiacol was the main volatile phenol (Tanguler et al., 2017).

| Lactones
Considering the total concentrations of lactones, Shalgam-175PC samples resulted in a greater amount of lactones (143.63 μg/L) in all samples.On the other hand, the difference between the other samples was found to be statistically insignificant (p > .05).A total of 6 lactone compounds were identified and quantified in all samples.
γ-Nonalactone, with a sweet, coconut-like aroma, was the main lactone, and its amount was higher in Shalgam-175 BC (73.1 μg/L) than the others.Moreover, this lactone nearly accounted for 43-65% of total lactones in all samples in the present study (Table 1).

| Naphthalenes
Naphthalene can occur during the dehydration and cyclization of hydrocarbon compounds under a certain temperature, or it can be formed by the degradation of fruits/vegetables by some microorganisms present in the medium.Naphthalenes have been reported to be responsible for the phenolic odor, which is generally accepted as unpleasant (Li et al., 2021;Tanguler et al., 2017).
In a previous study (Tanguler et al., 2017) on the ACs of shalgam with different production methods, three naphthalenes (naphthalene, 2-methyl-naphthalene, and 2-ethyl-naphthalene) were found, and their values are consistent with the values determined in the current study.On the other hand, components such as naphthalene, 2-methyl-naphthalene, 1-methylnaphthalene, and 1,6-dimethyl-naphthalene have been detected in foxtail millet varieties (Li et al., 2021).

| Other compounds
Norisoprenoids can form by degrading aromatic carotenoids like beta-carotene and neoxanthin directly, or they can be stored as glycoconjugates that can subsequently release their volatile aglycone during fermentation through enzymatic and acid hydrolysis processes.These compounds, which have low detection thresholds, are particularly characterized by imparting floral and woody odors to fermented foods/drinks (Mendes-Pinto, 2009).
3-Hydroxyβ-damascenone, a norisoprenoid previously identified in shalgam, has a very low detection threshold.This compound has a significant effect on the aroma compounds of food and drinks.
In a previous study, 3-hydroxyβ-damascenone as a norisoprenoid was defined, and its amounts were reported to be between 37.5 and 69.2 μg/L (Tanguler et al., 2017).Similarly, in our study, it was determined between 47.5 and 55.1 μg/L (Table 1).In contrast, 3-oxoα-ionol was detected for the first time in shalgams.
In the present study, the total amount of aldehydes and ketones changed from 46.7 (Shalgam-100PC) to 62.5 μg/L (Shalgam-175PC; p < .05).Similar to norisoprenoids, aldehydes and ketones were found to be the least dominant compounds in number and amount compared to other aroma compounds.4-hydroxy-4-methyl-2-pentanone and heptanal were detected in trace quantities (45.5-61.1 and 1.14-1.48μg/L, respectively).Statistical differences were observed with a slight variation in the 4-hydroxy-4-methyl-2-pentanone and heptanal concentrations of the samples with varying amounts of purple carrots (p < .05;Tables 1 and 2).Guler et al. (2015) detected 3 aldehydes, acetaldehyde, hexanal, and octanal, in all carrot cultivars.In another study, 3-hydroxy-3-methyl-2-butanone, 3-hydroxy-2-butanone, 1-hydroxy-2-propanone, furfural, and nonanal were identified as carbonyl compounds in raw, colored carrots, and their total concentration was determined to be 569 μg/kg (Keskin et al., 2021).Keser et al. (2020) reported that the dominant aldehydes in carrots are hexanal, heptanal, and octanal.Similarly, Polat et al. (2022) found furfural in processed carrots in addition to hexanal, heptanal, nonanal, and 3-hydroxy-2-butanone determined in raw carrots.In research, the presence of 3 aldehydes and 4 ketone compounds in shalgam was reported (Kirlangic et al., 2021).Also, other studies reported the presence of hexanal and heptanal as aldehydes and 4-nonanone, 4-hydroxy-4-methyl-2-pentanone, and 2-heptanone as ketones (Ekici et al., 2021;Tanguler et al., 2017).In this study, production significantly affects ACs both quantitatively and qualitatively.Furthermore, the maximum total amount of ACs was produced with the addition of 200 g/L purple carrot.Moreover, twenty-eight ACs were detected for the first time in shalgam, including 7 terpenes, 7 esters, 3 alcohols, 4 volatile acids, 3 volatile phenols, 1 lactone, 1 norisoprenoid, and 2 naphthalenes.In this respect, the new findings obtained within the scope of this study have the potential to benefit the shalgam-producing industry and researchers who strive to improve the nutritional value, processing, and marketing of shalgam.In particular, it can give producers an idea of how much carrot to use in production in terms of aroma, which affects the appeal of consumers.However, there is a need to conduct various studies, especially on the extent to which the fermentation process will affect the shalgam beverage ACs affected by the addition of purple carrots.
For example,Guler et al. (2015),Keser et al. (2020),Keskin et al. (2021), andPolat et al. (2022) reported that approximately 33 different ACs (terpenes, alcohols, aldehydes, ketones, acids, and esters) were detected in carrots of different colors, and the main ACs were terpenes.In the current study, because of fermentation and biochemical reactions, some new compounds, such as alcohols, were formed in shalgam.While the ACs of all shalgam samples were generally similar, the total ACs amounts were different.The concentration of ACs in the samples varied between 5472 μg/L (Shalgam-125 BC) and 6490 μg/L (Shalgam-200 BC; Table2).In previous research on the effect of different production methods on the ACs of shalgam, the ACs concentration was found to be 3162-4918 μg/L(Tanguler et al., 2017).Kirlangic et al. (2021) determined the AC concentration of shalgam at the beginning of storage as 1559-2180 μg/L.Similarly, it was reported as approximately 2230 μg/L in another study conducted byKirlangic et al. (2021).
aldehydes and ketones were determined, and their amounts are consistent with previous studies.Principal component analysis (PCA) was applied to construct a model to classify shalgam samples according to aroma groups.As seen in the biplots (Figure2), the PCA model, which consists of two main components, explains 82.16% of the total variance (F1: 43.90%, F2: 38.26%).According to the biplot of the aroma groups, Shalgam-125PC, Shalgam-150PC, and Shalgam-175PC samples are on the left, and Shalgam-100PC and Shalgam-200PC samples are on the right.It has been determined that the correlation between the location of the shalgam samples and the aroma groups is important in the coordinate system.Shalgam-150PC and Shalgam-175PC samples showed a dominant character in terms of norisoprenoid, aldehyde, and ketone compounds.Similarly, higher alcohol compounds, terpenes, and esters were found to be dominant in the Shalgam-200PC sample.The Shalgam-125PC sample, on the other hand, showed a more dominant character in terms of volatile phenol and volatile acid compounds compared to the other samples.Therefore, it is seen that the effect of adding different amounts of carrots to the ACs in shalgam is significant.4| CON CLUS IONOne of the most important results obtained in this study is that the use of different amounts of purple carrots during shalgam F I G U R E 2 Principal component analysis (PCA) biplot of shalgam samples.Shalgam-100PC, 100 g/L purple carrot addition; Shalgam-125PC, 125 g/L purple carrot addition; Shalgam-150PC, 150 g/L purple carrot addition; Shalgam-175PC, 175 g/L purple carrot addition; Shalgam-200PC, 200 g/L purple carrot addition.

TABLE 1 (
Tanguler et al. (2017)ndKirlangic et al. (2021),Ekici et al. (2021), andKirlangic et al. (2021)defined terpenes, alcohols, ketones, and aldehydes as ACs in shalgam and stated that the main groups of ACs quantitatively were terpenes and alcohols.Tanguler et al. (2017)determined the effect of starter culture addition on ACs with traditional and rapid methods by the GC-MS-FID method.Ekici et al. (2021) used